Allison 1000 & 2000 Gen 5 Fault Code:P0725 Engine Speed Sensor Circuit

CIRCUIT DESCRIPTION:
The speed sensors are devices which convert mechanical motion to an electrical signal. This test detects an output speed sensor circuit short to battery, ground, or open.

ACTION TAKEN WHEN THE DTC SETS:
When DTC P0720 is active, the following conditions occur:
1. DTC P0725 is stored in the TCM history.
2. The TCM does not illuminate the CHECK TRANS light.
3. If ignition is OFF, then engine speed is set to 0. If turbine shaft speed is greater than the engine speed calibration default value, then substitute turbine shaft speed as engine speed.

CONDITIONS FOR CLEARING THE DTC:/CHECK TRANS LIGHT
Use the diagnostic tool to clear the DTC from the TCM history. The TCM automatically clears the DTC from the TCM history if the vehicle completes 40 warm-up cycles without the DTC recurring.

DIAGNOSTIC AIDS:
DTC P0725 may be caused by:
1. W139 and/or W159 shorted to another wire in chassis harness or to ground.
2. W139 and/or W159 high resistance or open circuit.
3. Broken or defective connector assemblies allowing pushed back pins to short together.
4. Unlocked connectors, missing seal plugs allowing moisture in connectors.
5. Fatigued wires at speed sensor connectors (broken strands).
6. Incorrect pin crimps or expanded terminals.
7. Defective engine speed sensor.
8. Defective TCM.
9. Wire pair not twisted or not sufficiently twisted.

NOTE: Inspect that the speed sensor wiring consists of twisted pairs at the rate of 12 to 16 twists per 300 mm. These twists must extend the entire length of the wiring harness to within at least 50 mm of the speed sensor connector.

NOTE: The OEM transmission warranty, or the extended coverage for parts and labor, does not cover the repair or replacement of OEM or bodybuilder-provided components or any external wire harnesses not provided by the OEM.

Before repairing or replacing these components or circuits that caused a transmission issue, always contact the vehicle OEM call center and/or the vehicle OEM or bodybuilder service representative to verify the warranty coverage and proper payment arrangements, arrange an alternate sublet or repair plan (if needed), and get troubleshooting assistance for the repair (such as vehicle schematics, DTC trees, parts assistance, etc).